Special counsel Robert Mueller is recommending a judge sentence one-time Donald Trump campaign aide George Papadopoulos to up to six months in jail for lying to the FBI, a request that includes a strong rebuke of a man who allegedly failed to assist with the investigation into Russian interference in the 2016 elections, according to documents filed with the court.

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Prosecutors did not make a specific recommendation but urged the judge to give Papadopoulos jail time and said a sentence within the guideline range of up to six months imprisonment was "appropriate and warranted."

The government said he should be held accountable for having repeatedly misled them “about critical facts, in an investigation of national importance, after having been explicitly warned that lying to the FBI was a federal offense. The nature and circumstances of the offense warrant a sentence of incarceration.”

Papadopoulos, who had served as a volunteer to the Trump team, traveled as an emissary from the campaign to foreign leaders in the Middle East and the Mediterranean. In July 2017, he was charged with lying to the FBI about his contacts during the campaign with a professor who had “substantial connections to Russian government officials," and accused of trying to conceal his contacts from the FBI.

This undated image posted on his Linkedin profile shows George Papadopoulos posing on a street of London.

Court records filed by special counsel Robert Mueller describe how the professor approached Papadopoulos after learning of his role in the Trump campaign. The court filing does not name the professor, but he has since been widely identified as Joseph Mifsud, then the director of the London Academy of Diplomacy. ABC News has been unable to reach Mifsud for comment.

The professor told Papadopoulos the Russians had “dirt” on Democrat Hillary Clinton in the form of “thousands of emails” that they had procured, according to the court documents.

Papadopoulos reportedly bragged about that offer to an Australian diplomat, who then tipped off the FBI and launched that agency’s counterintelligence investigation into possible collusion between the Trump campaign and Russia.

Papadopoulos was arrested by the FBI when he arrived at Dulles International Airport in July 2017 and charged under seal. He agreed to cooperate with investigators in exchange for a lighter sentence.

The government’s sentencing recommendation includes clear signs the Mueller team felt betrayed by Papadopoulos after he struck a plea agreement and pledged his full cooperation.

The filing says Papadopoulos repeatedly withheld key details about his contacts with Russians and neglected to turn over the cell phone he used to communicate with Mifsud until the government expressly asked for it.

“His lies negatively affected the FBI’s Russia investigation, and prevented the FBI from effectively identifying and confronting witnesses in a timely fashion,” the filing says. “His lies were not momentary lapses. He lied repeatedly over the course of more than two hours, and his lies were designed to conceal facts he knew were critical: the importance of the information he received from the Professor, and his own communications and contacts with Russians and Russian intermediaries during the Trump campaign.”

The filing also says that, even after his initial FBI interview, Papadopoulos made repeated attempts to land jobs with the fledgling Trump administration, including a high level post with the National Security Council.

“In the hours after being interviewed by the FBI, the defendant submitted his biography and a description of work he did on the campaign in an effort to obtain a position as a Deputy Assistant Secretary in the Energy Department,” the filing says.

Papadopoulos continued to deceive Mueller investigators during a critical period in early 2017, when Mifsud was visiting Washington, D.C., and could have been detained and questioned effectively. “The defendant’s lies undermined investigators’ ability to challenge the Professor or potentially detain or arrest him while still in the United States,” it says. “The Professor left the United States on February 11, 2017 and he has not returned to the United States since then.”

Papadopoulos’s legal team will file their own sentencing assessment to the court in two weeks, and is expected to ask for probation.

The sentence recommendation comes as Simona Mangiante Papadopoulos has mounted the latest in a series of publicity campaigns – this one suggesting her husband has misgivings about his plea agreement.

Obtained by ABC News

George Papadopoulos married Simona Mangiante in Chicago, March 2, 2018.

Back in December, in an interview with ABC’s George Stephanopoulos, she had described her spouse as the "John Dean" of the Russia probe, a reference to the Watergate-era former White House counsel who pleaded guilty to conspiracy to obstruct justice and became a key witness against President Richard Nixon and his aides.

“George is very loyal to his country,” she said at the time. “He is already on the right side of history. I think he will make a big difference.”

Earlier this month, Papadopoulos received a sealed sentencing document prepared for the court. After that, the defendant’s wife began an aggressive media blitz in which she strongly hinted her husband is considering changing lawyers and rescinding his plea deal.

After appearing before Democratic members of the House intelligence committee earlier this summer, she said that Papadopoulos has come to believe the professor may have been working for Western intelligence agencies and set him up.

"I actually never said explicitly that it was an entrapment from the FBI. I just said that he definitely was...the target of a different set-up," she said.

In June, the Daily Caller News Foundation reported that Simona Papadopoulos said, "It looks to be one among a series of attempts to entrap George," adding, "The question today to me [is whether] these people are simply shady businessmen or are they part of a greater attempt to entrap George in illegal activity.”

Since her husband’s guilty plea in exchange for cooperation with the Mueller probe, Papadopoulos has been living in Chicago. Federal investigators have imposed restrictions on his travel until his sentencing, which is now scheduled for September 7.